Thesis subject

Forensic Science: Finding the environmental source for Legionella pneumophila sequence type 47


Legionella pneumophila is a bacterium that can cause life-threating pneumonia (Legionnaire’s disease). Around 350 people attract Legionnaire’s disease each year in the Netherlands and about 15 to 30 people die of this disease each year. When Legionnaire’s disease is discovered in a patient, efforts are made to cultivate the causative L. pneumophila strain from the patient. When a patient strain is isolated, the L. pneumophila strain is genotyped using multilocus sequence based typing (MLST), which is the standard method in Europe to do epidemiological L. pneumophila research. In the Netherlands, sequence type ST47 is the dominant sequence type and observed in approximately 1/3 of the patients. Furthermore, it is obligatory in the Netherlands to do an environmental source investigation once a L. pneumophila strain is isolated from a patient. In that case, based on results from a questionnaire with the patient, known environmental sources of L. pneumophila (e.g. drinking water, sauna, swimming pools, car wash, cooling towers) are sampled for cultivable L. pneumophila. If L. pneumophila is cultivated from a possible source, then the ST is determined with MLST and compared with the ST of the patient strain. The results from this obligatory environmental source investigation are disappointing, since a match is find in only a few cases. This means, that although L pneumophila ST47 is observed regularly in patients, the environmental source of L. pneumophila ST47 is still known. Recently, French/British collaborative research groups have developed a qPCR method for the specific detection of L. pneumophila ST47. By using this test, it should be possible to detect whether L. pneumophila ST47 is present in suspected and new environmental sources.


Identify traditional and new environmental sources for L. pneumophila and, subsequently, sample these environmental sources and analyse the presence of Legionella spp., L. pneumophila and L. pneumophila ST47 by using traditional (selective agar plating) and molecular (qPCR, NGS, MLST) methods as forensic tools to identify the environmental source for L. pneumophila ST47.

More information

The project is designed for BSc or MSc thesis, to be carried out at the Laboratory of Microbiology, Wageningen University, in collaboration with KWR Watercycle Research (Nieuwegein).

If you are interested, please contact Paul van der Wielen via or